the only thing that you can do with sony firmware is go up....for instance:

3.10>>3.11>>3.30
this is the only order that you can go in with sony firmware above 3.03..

CFW is not an option for you at all what-so-ever right now......not feasible...
you have to wait for a downgrader before you can install any OE on your psp....as you can only install CFW from sony 1.5, or another CFW